Retinitis due to Rickettsia infection

Abstract

A 67-year-old woman with type 2 diabetes presented to our hospital with decreased left vision for 7 days. On examination, right visual acuity was 20/30, and left visual acuity was 20/50. Intraocular pressures were both normal. Anterior chambers were deep and uninflamed, with bilateral nuclear sclerotic cataracts. There was mild left vitritis, but none in the right eye. Right fundoscopy was normal. Left fundoscopy showed one-disc diameter of unifocal retinitis along the superior vascular arcade (figure A). Left fluorescein angiography revealed late staining in the area of retinitis. The patient was treated presumptively with anti-toxoplasmosis and anti-herpes therapy (oral pyrimethamine [100 mg for the first day then 50 mg daily] and oral sulfadiazine [1 g three times daily] for toxoplasmosis, and intravenous aciclovir [800 mg three times daily] for herpetic retinitis), while awaiting laboratory results. PCR testing of anterior chamber taps were negative for Herpes simplex virus and toxoplasmosis. Negative Treponema pallidum hemagglutination and venereal disease research laboratory test excluded syphilis. Negative QuantiFERON-TB Gold test and tuberculin skin test were negative, and eliminated tuberculosis as a possible cause. Serum angiotensin converting enzyme and lysozyme were normal, which made sarcoidosis an unlikely explanation for the clinical findings. The patient's vision worsened to 20/200 in the left eye. Fundoscopy showed ongoing retinitis with a new retinal haemorrhage and serous macular detachment. She subsequently disclosed having episodes of malaise, headache, myalgia, skin rash (figure B), and fever (maximum 39·5°C; unresponsive to amoxicillin 500 mg three times a day), following travel to rural Algeria. Serology for Rickettsia conorii showed an elevated IgG titer of 1024 g/L, but was negative for IgM. Anterior tap PCR and cutaneous biopsy were negative for Rickettsia. Fundoscopy improved markedly after 7 days of treatment with doxycycline (200 mg daily). After 2 months, visual acuity was 20/20 and the retinitis resolved fully. This case illustrates the importance of careful history taking, and maintaining an index of suspicion for Rickettsia in patients who have travelled to an endemic area and present with fever, skin rash, and retinitis.